Proportional slide rule



Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE PBOPORTIONAL SLIDERULE y Bartolomeo Ferrughelli, New York, N. Y. Application March 9,1938, Serial No. 194,742 n 1 Claim.v (Cl. 1635-70) This inventionrelates to slide rules, for use by uated bar It are elastic strips 40,such as rubarchitects, artisans, engineers, mechanics and ber. thesestrips being confined to the slide 20 others engaged in work requiringscale measure-v and head 38 at their respective ends, as best ments.seen in Figure 1.

5 It is an object of the invention to provide a These strips beargraduations 4I-42 respec- 5 rule readily settable and unusuallyaccurate, certively and can be read in connection with the tain of thegraduated scales being composed off graduations on the bar I8. elastic,contractile material. The effect of the elastic strips is to maintain Afurther feature is in the provision of a pluthe slide 20 against a stopM, set in the channel,

1 rality of Well defined stops of definite accuracy, or if the slide isdrawn outwardly, maintain the 10 which avoid the danger of accidentaldisplaceslide carried pawl 26 in contact with any of the ment aftersetting. teeth 3I to which it may be adjusted.

Another purpose is to produce a rule provided Thus the rule may be usedby artisans where an with scales the normal graduations of which mayenlarged or diminished scale must be employed,

be uniformly varied with respect to spaced resuch for instance aspattern makers, and archilation. tects who ordinarily employ what isknown as These and other objects are accomplished by shrink rules inwhich the scale is proportionthe novel construction and arrangement ofparts ately increased over that which is normal.

hereinafter described and illustrated in the ao- To use the presentslide rule in which the excompanyng drawing, constitutinga material parttensible members 40 are graduated to read to 20 of this disclosure, andin which: one-half the scale on the rigid bar I8, it will be Figure 1 isa top plan view` of an embodiment apparent that a reduction of 2 to 1 isits normal of the invention. condition; if the members 4I) be stretcheduntil Figure 2 is an edge view of the same. the index numerals I-I arein register the scales Figure 3 is an enlarged cross sectional view willbe alike, while if the numeral I on member 25 taken on line 3 3 ofFigure l. l0 be brought to register with the numeral 2 Figure 4 is asimilar sectional view taken on on the rigid scale, a proportion of 1 to2 is obline 4-4 of Figure 1. tained, or in other words, a double size isindi- Figure 5 is a further enlarged fragmentary cated. longitudinalsectional view taken on line 5-5 Asy an example in the use of the scale,let it 30 of Figure 1. be assumed that a drawing is to be reduced inReferring to the drawing in greater detail, the size so that 7 inchesequals 12 inches of the numeral I5 designates a pair of thin bars heldoriginal. The edge of the slide 20 is placed at the in clamped relationat their ends by the riveted 'l inch mark on the scale 35 of thepermanent jaws I8 of a bowed handle I1. or ilxed bar It, thereby the l2inch scale o! the 35 Fixed centrally between the bars I5 is a broadelastic scale 40 will have been reduced to a scale blade I8 extending toa considerable disproportionof 'I to l2. tance ODDOSiielY Outward withrespect i0 the Obviously lother similar proportions can readhandle. lily be attained.

40 A slide 20 is mounted to move along vthe bar Having thus describedthe invention, what is 40 i8, the Slide having lateral rele 2| i0 PrO-.claimed as new and sought to secure by Letters vide an eiilcient grip.Patent, is:

A raised housing 22 on the upper surface oi the A proportionate rulecomprising a thin, nat slide carries a .lever 23, pivoted at 24, one armrigid graduated straight scale bar having a cen- 5 Of the lever having aknob 25 projecting ythrough tral longitudinal channel throughout itsentire 46 the raised cover oi the housing. the other arm length on oneside thereof, ratchet teeth disterminaiihg in a NW1 23 Dresseddownwardly posed transversely in said channel in uniformly by a Spring21- spaced definite relation, a slide movable on said The centralportion of the bar I8 has a longiscale, a spring pressed manuallyoperable pawl tudinal channel 30 in which are formed ratchet pivoted insaid slide selectively engageable with 50 teeth 3l engaseable by thepawl as the slide `2li said teeth, a cross bar nxed on one end of saidis drawn outwardly, the teeth being accurately scale, a loop handlecombined with said bar, elasspaced to agree with the graduations on thescale. tic scales nxed at their respective ends to said l The bar I8bears graduations 35-35 on its slide and bar, parallel and closelyadjacent said upper Side. adjacent its respective edges, whichstationary scale, and series oi graduations on said 65 are preferablybevelled, as at I1, and is ilrmly elastic scales normally half thedistance apart secured in the head n formed by the bars to as thegraduations on said stationary scale. which the handle I8 is attached. i

spaced outwardly from the edges oi the grad- BARTOLOMEO FERRUGBEILI.'

